1. Field of the Invention
This invention relates generally to information signal recording and reproducing appparatus and, more particularly, is directed to a tape speed control circuit for an information signal recording and reproducing apparatus.
2. Description of the Prior Art
Generally, video tape recorders (VTRs) are provided with tape tension control apparatus for maintaining the tension of the tape between the supply and take-up reels at a constant value when the speed of advancement of the tape is increased or decreased. In such case, however, the acceleration of the tape extending between the supply and take-up reels may not be constant, which may result in various problems.
For example, many VTRs are adapted to perform an editing operation. In such case, the tape speed may vary during the operation in which a search position on the tape is to be detected for use in the editing operation. Thus, if the tape speed is ten times the normal tape speed, that is, in a fast search mode, the tape speed may have to be increased to an extremely fast speed, for example, sixty times the normal tape speed, to shorten the time for detecting the search position during the editing operation. When the search position is approached, the tape speed is automatically decreased to stop at such position.
It is to be appreciated that, during the editing operation, if the acceleration or deceleration of the tape is not constant, the period during which the tape reaches a desired speed will vary. For example, during deceleration, the braking force applied to the drive motors for the take-up reel and/or supply reel, and therefore the braking time within which the tape is brought to its desired speed during the deceleration operation, cannot be accurately controlled. In addition, the amount of braking force depends on the diameter of the reel which is used and the amount of tape thereon, which makes the aforementioned control more difficult.